CA2047991A1 - Solid contact system for potentiometric sensors - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

An improvement to the coated wire electrode has been accomplished via inclusion of a fortiophore into a sensor device. Sensor devices of the present invention include: an internal reference element; a membrane; and a fortiophore.
Fortiophores are neutral charge carriers, which complex reversibly a corresponding ion of the conductive material used at the internal reference element. The fortiophore provides an electrochemically defined and reproducible solid internal contact between the membrane and the internal reference element. This solid internal contact, for example, in ion selective sensors, provides more reproducible potential offsets and better precision, and faster wet up. The fortiophores can be utilized in other electrochemical devices.

Description

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SO~ID CONTACT SYSTEM ~OR POTEN~IONETRIC SENSORS
BACXGROUND OF THE INVENTIQN

1. Field of the~In~en~ion: The pre~ent i~vention relates to ~en~or de~ice~, and more particularly, potentiometric sensors - comprising an internal reference el~e~t, a membrane, and a fortiophore. ~he fortiop~ore~ an electrooh~mical ag~nt, inter~aces the membrane and ~he internal re~erence element to form a solid in~ernal contact.

2. Teahnical Revle~_ Conventional 6ensor. (3) known in the art (FIG. 1) have a layer of metal, e.g. Ag or other electrioally conductive material, a layer o~ meta} halide, e.g. AgCl, an aqueous or dry inter~al ~illing ~olution (u~ually containing the chlorids ~alt of ~he aation being analyzed, e.g. XCl), and an ion ~elective membrane. See ;. genera}ly Workinq with Ion-~alective Ele trodes, Camman, Ko .. Springer-Verlag, 1979. The ion ~electiYe memhrane includes an ionophor~. See Ammann et al. Helvetica ACTA 1975, 58~
1535-1548. An ionophore is an ion-~elective compound which is pe~mselectiva, e.g. capable of complexing a desirlsd ion and extracting it without a counterion into the inter~aaial zone of the membrane. The internal filling so~ution can form eleatrochemically dafined inter~aces with the metal halide on one side and the ionophore doped in the membrane. Such , ~ . . ,; : .. . . - ~

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internal filling solution~ actually aontain a con~tant activity of the communicating ions which provide a high and dominating exchange current at both inter~aces and therefore constant and predictable potentials at both the metal halide and the inner surface of the membrane. The outer surface of the membrane is exposed to the test sample. The potential generated at this inter~ace is, according to the Nernst equation, dependant on the activity o~ the test sample ion, which the membrane i8 ~elective ~or.
Coated wire eleotrodes (CWE) h~ve a layer of Ag or o~her conductive ~aterial, an optional layer of AgCl, and an ion fielective membrane. See generally ohapter ~our of Princi~les of Chemical Sensors, Janata, J.~ Plellum Pres~, 1989. There is no internal fill olution to interface the ~gCl with ~he 15 membrane to maintain the con~tant potential a~ in the conventional electrodes. The potential i~ therefore determi~ed by unXnown interfacial charge exchange agents or sites of uncontrolled activities. Potential measurements for the CWE tend to dri t, have a 610W response ti~e, and have 1 20 unreproducible potential o~f~ets due to the unde~ined interface between the membrane and electrochemical internal re~erence. In addltion, any minute a~ounts o~ wat~r ~oluable 6alt at the interface will cause water uptake aausing dri~t in potential.
In attempting to reduce an ion selective sensor to a miniaturized planar aon~iguration, problema ~rise due to di~erences in storage and measuring co~dition~. Water will permeate the membrane at any time to maintain osmotic balance~ X~ water permeates from the sample into the internal electrolyte, the membrane will bulge or it may burst. If water leaves (e.g. evaporation) the sensor, the membrane will crenate. Moreover~ this would change the ac~ivity of the internal electrolyte ~olution, thereby causlng potential drift. This relationship is not considered in larger conventional electrodes because of the large reservoir o~
internal fill solution, but in a small sensor such as made by planar processing technologies, it becomes critical.

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Shono et al., U.S. Patent Nos. 4,554,362 and 4,523/994, describe the use of bis-crown-ether derivative~ a~ neutral carriers in ion-selective membranes o~ ion~elective electrodes.
Delton et al., U.~. Patent No. 4,504,368, describe the use of crown-ether compositions as ionophores in ion-~elective compositions and electrodes. Variou~ ~olven~s are disclo~ed to solvate the crown ether and to provide ion moblli~y in the membrane.
Battaglia et al., U.S. Patent No. 4,214,96~, describe dry-operati~e ion selective electrodes incorporating the use of ionophores.
Freiser et al., U.S. Patent No. 4,115,209 de cribe an electrode ~ormed by coating a condu tive substrate with an ion exchange material in a matrix. A li~ting o~
potentiometrically mea~urable ion or group of ion i~
provided~
;~ Baginski et al., EP O 267 724, disclose a method o~
printing an electroch~mically acti~e material on a su~strate 2~ to provide a te~t dev~ce for carrying out a ~icrochemical test.
Oue et al., Che~. Ltr. 1988, 409 410 disclo~e the use of monothiacrown ether ~MTCE) as a neutral carrier ~or Ag-selective electrodes. It is noted that Que in a letter dated 9-6-88 recommended that if the compound is ueed as a neutral silver ion carrier, it should be first complexed with AgN03 in order to reduce conditioning time.
Daunert et al., Anal. Chem. 1990, 62, 1428-1431 describe ion-selective electrodes inaluding an ionophore covalently attached to a polymeric matrix.
Oue, M. et al., J. Chem. Soc.-Perkin Trans. 1989, 1675-1678 disclose the use of lipophilic mono-and di-thiacrown ethers as neutral carriers of polymeric membrane Ag~-selective electrodes.
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, ~ -4- ~3ll79 SUM~RY OF THE INYENTION

In general, the present invention i~ directed to a sensor device formed of an internal reference element having an electrically conduc~ive sub~rate; a membrane; and a - fortiophore. A controlled solid electrochemical inter~ace between ~he membrane and the internal re~erence ele~ent i8 . maintained by the fortiophore. The ~ortlophore form~ a : complex with the conductive ion, e.g. metal, o~ the eleatrica~ly conductive ~ub~trate which pro~ide~ a true and reproducible electriaal ~olid internal con~aat between the membrane and the electrically conduc~ive su~rate. ~he membrane includes an ionophore which ~orme a complex with an :: ion in a test sa~ple and form~ the e~ectrochemical interface :- 15 of the membrane with the te~t 8ampl~0 The 8~n80r device may ~: be constructed in various ~orm6~ e.g. planar, coated wire, - ISFET; which depending on!the ~orm chosen may xequire a base ~ component. In one embodiment a planar ~en~or i~ ~ormed of an : internal re~erence element prin~d on a base o~ ~uitabl~
non-conductive mat~rial with a m~mbr~ne di~po~ed over the internal re~eren~e element and a fortiophore.
:: In contrast to a neutral ionophore, the fortiophore i~ a neutral complexing agent which doe~, but does not need, to be : ion-selective. Its only purpose is to provide a reversable electrochemical co~unication wlth the internal ele~ent. It `- does not interface with the electrochemical action of the ionophore at the sample/membrane interface.
: ~he use of a fortiophore allows ~ox the elimination o~ two ~: layers, the metal halide and the liguid or dry internal fill, from the conventional sensor configuration (FIG. 1). The resulting sensor of the pre~ent invention (FIG. 2) aomprise~ a two layer system, which i8 ea~ier to manu~aature. Another advantage is that the sensor i8 not water susceptible due to the absence of an internal electrolyte fill.
It is noted that the terms sensor and chip in the specification and claims are used inkerchangeably.
It is to be understood that the representations in the FIGS. 1-5 are diagrammatic and that no attempt has been made to indicate actual scales or ratios.

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Accordi~gly, it i~ a primary object o~ the present invention to provide a two layer ensor device having an internal reference element and a membrane, which are electrochemically interfaced by a ~ortiophore.
It is another object o~ the in~ention to provide an ion ~elective 6ensor comprising an internal re~erence element, an ion selective membrane, and a fortiophore; the membrane including an ionophore. The for~iophore forms a complex with the metal ion of the internal reference ëlement and therefore pro~ides a solid internal contact bet~een the internal reference element and the membrane to interface the membrane with the internal reference element. The ionophore ~orms a complex ~ith an ion in a test ~ample to inter~ace the membrane with the test sample.
~ still ~urther ob;ect o~ ths invention is to 1provide ion selective sensor~ which have more reproducible ~tandard potentials, better preci~ion and faster wet up.
It is a still further object of the invention to provide a planar potentiometria sensor.
! 20 It i~ another o~ect of the invention to pr~vide a aoated wire sensor.
Another object of the invention is to provide a reproducible ~olid ~ate contact for ISFET sensor.
Still another object of the present invention is to provide a sensor design to facilitate mas~ ~anufacturing of sensors which exhibit sen~or to 6ensor reproducibility and a ~

long shelf life.
A further object of the invention is to provide a sensor deviae including a fortiophore and at least one ionophore.
With these and other objectives in view, as will be apparent to those skille~ in the art, the invention resides in the combination o~ materials set ~orth in the speci~ication and aovered by the claims appended hereto.

ABBREVIATIONS
The following abbreviations are used in the specification, accompanying tables and claims:

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THF Tetrahydrofuran VAL Valinomycin PVC Poly (vinylchloride) K~B Potassium tetraphenyl borate 5 ~O~M ~rioctyl trimellitate UDCN Undecyl ayan~de DTCE 1,10-Dithia-18-cro~n-6-ether MTCE Dodecyl-16-crown-5-1ether AgTpClPB Silver ~etra~i~ (p-chlorophenyl) borate BHTCH Tetra~n-hexy1-3,3',4,4'-benzhydrotetracarboxylat2 ONPOE o-nitrophenol octyl ether SHONO Bis (12-crown-4~ me~hyldodecyl m,alonate TD~A ~ridodecylamine 15 ~TH 1001 (-)-(R,R)-N,N~-~BIS~ ethoxycarbonyl) undecyl]-N,N~-4,5-t~tramethyl-3,6-dioxaoctane dia~iae KTpClPB Po~assi~m tetrakis (p-chlorophenyl3 borate 20 AgB~NZ Silver Benzoate DUP Diundecyl phthalate E~H 2120 N,N,N',N'-Tetracy¢lohexy1-1,2-- phenylenedioxydiacetamide IFSE~ Ion-~ensitive field e~fect tran~istor : BRIEF DESCRIPTION OF THE DRAWINGS
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FIG. 1 is a sectional ~chematic view o~ a conventional elactrodQ device.
FIG. 2 is a sectional sohematic view of a potentiometric device constructed in accordance with the present invention.
FIG. 3 is a sectional schematic view o~ a coated wire type sensor constructed in accordance with the present invention.
35FIG. 4 is a sectional schematic view of a planar type sensor constructed in acaordance with the present invention.
FIG. 5 is a sectional schematic view of a ISFE~ type sensor constructed in accordance with the present invention.

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FIG. 6 is a graph ~howing wet up results ~or ~hip 2-6-1.
FIG. 7 is a graph ~howing differential measureme~t results ~or chip 2-6-1.
FIG. 8 i~ a graph ~howing wet up result6 for chip 2-19-1.
FIG. 9 is a graph showing wet up re~ult6 for chip 2-6-7.
F~G. 10 is a graph showing wet up re~ult~ for chip 2-19-4.
FIG. 11 is ~ graph showing wet up result~ ~or chip 2-39-~0 in response to potassium.
FIG. 12 i8 a graph showing w~t up results ~or chip 2-180-3 in re6ponse to potassium.
FIG. 13 is a graph ~howing wet up resul~ for chip 2-53-10.
FIG. 1~ is a graph showing wet up results ~or chip 2-53-9.
FIG. 15 is a graph ~howing wet up re~ults for ~hip 3-62-1 in response to calcium.
FIG. 1~ is a graph ~howing wet up results for chip 30050~1 ~or pH measurement.
FIG. 17 i~ a graph o~ wet up results for chip 5-15--2 for sodium mea~urement.
q 20 ~IG. 18 i~ a graph show1ng wet up re~ult~ ~or chlp 129-32-1 for pota~ium measurement.
FIG. 19 is a graph showing wet up result~ for chip 53-17-1 for potassium measurement.
FIG. 20 is a graph ~howing wet up results ~or chip 25 129-34-6 for potassium ~easurement.
~' DESCRIPTION OF THE PRE~ D EMBODIMENT

Referring to FIG. 2 sen~or devicQ ~) o~ the present inventlon includes a ba~e aomponent (lOj which i~ comprised of an inert substrate; an internal reference element (12~; and a membrane (20). There are many factors to be considered in selecting an inert substrate as generally described in chapter 4 of the Randbook o~ Thick Film HYbrid Microelectronics, C.A.
Harper, McGraw-Hill Book Company, Reis~ue, 1982.
one con~iguration of the substrate (10) for the sensor device is a plane. The preferred composition of the substrate :

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in the planar sPn60r device, FIG. 4, i8 alumina. The ~ze of the plane wi}l vary in accordance with the num~er of internal re~erence elements deposited onto the ~ub6trate, the design re~uirements attendant for various applications o~ the chip and the manufacturing consi~erations of prod~cing the chips.
The ~nternal re~erence element (12) O:e the pr~ferred embodiment are ~lectrically conductive ~ubstrate~; e.g.
metals, alloys or a non-~etal and me~al or alloy mixture, etc.
Alternatively, another embodiment of the CWE txpe (6) of 10 the ~en~or device comprising a wire (12) w$th expo~ed tlp (13) shown in FIG. 3: with the membrane (20) being depo~ited on the exposed tip of ~he wire.
A sensor device integrated with ~icroelectronic ele~ents, e.g. ISFET (7) i~ shown in FIG. 5. The ISFE~ mounted on a 15 base ao~ponent (11) includes a BilicOn ~ubBtrate ~24); a conduative material gate (26)7 a drai.n (28); a ~oura~ (30); an insulator (22), an encapsulatio~ zone (23); and a me~brane (20). See generally Ion Selec~ive Electrode~ in Analytical Chemistry, Yol~ 2, Freiæer, H., Plenum Pre~s, New York, 1979.
Referring to FI~. 4, one or mor~ electrically conductive leads ~14) are deposited on the sub~trate; ~aah of the conductive leads including a sensor site (16) and a contact area (18). The aontaat area pro~ides mea~ for being conneated to a mea uring device. The conductive lead i5 ordinarily compxised o~ a metal and an optional binder. The metal may consist of noble metals such as 6ilver, platinum, gold, palladium, iridium or alloys thereof, the choice of which depends on the per~ox~ance characteristias ~ought ~or a particular application of the ~ensor. Alternatively, the conductive substra~e include~ a mixkure o~ a non-metal substanae(s) and a metal or alloy. In the chips described below, silver is the preferred electrically conductive lead, unless otherwise stated.
An insulating material (22) is applied over a portion of the electrically conductive lead, see FIGs. 3-5. The insulating material is applied preferentially over a portion o~ the cond~ctive lead to separate 6ensor site ~rom the contaot area.

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, ~he ~nsulating material in ~he planar ~en~or t6 a dieleatric material. Other type of insulating mater~als are well known in the art; the use o~ which would depend on the t~pe and manufacturing requirements o~ the ~ensor device.
In the planar sensor embodlment o~ the present invention, a selected conductive lead a6 well a~ the insulating layer between the contact area and 6en~0r Bite are print2d onto the chip by convent~onal ~creen~ng and firing tech~ique~ the sensor device ~s an ion-6elective 6en or ~hen the membra~e that i~ applied to ~he sensor site is an lon-~eleatlve membrane. An ionophore i8 a component of the membrane of the sensor dPvice. ~he choice o~ ionophore will depend in part on the desired ion that iB to be analyzed by the sensor de~ic The printed chips may be optionally cleaned prior to the application of the ~embrane. One manner of clea~ing is as ~ollows: ~he chips are placed in a beaker co~taining 2-Propanol. The beaker i8 then plaaed in a heated, water-filled ultras~nic cleaner and sonicated ~or approximately 15 minu~e~. Next, ~he ahips are removed ~rom the beaker and rinsed wlth distill~d water. The conduct~ve substrate of the chips are wa~hed with a IM HNO3 solution for 30 second~, the~ rin~2d wi~h distilled water and dried in an oven at 100C for 1.5 hour~. Other means o~ cleaning the chips may be ut~lized and ar~ known by those ~killed in the art.
In some of the sensors, as noted below, the conductive substrate was chloridized prior to the application o~ the ion selective membrane (see Table 1 membrane cast on Ag/AgCl). A
.08% solution of FeC13 was applied ~o the chips for up to 2 minutes, then rinsed with distilled watex and blotted dry.
In one eensor device of the present invention, planar potassium sensor 2-39-10, the ion selective me~brane (See Table 1) was cast on blank silver electrodes on the chip. The membrane materials were first weighed into a glass vial, and 4.0 ml of THF was added. The resulting slurry was stirred until all the PVC dissolved. Then 0.01 g~ of silver salts was added and the solution stirred for an additional 1.5 hours.
The solution was then filtered usiny a 2 micron filter - 2 ~

(Milllpore). Next, aighteen drop6 o~ the reeulting ~embrane 501~tion were then cast onto the chip and the THF wa~
evaporated under controlled conditions, rendering a cured me~brane o~ about 50 micron thickness.
AlternativQly, instead o~ adding AgN03 (a~ the appropriate ~etal salt) the chip is soaXed for 12h in 100 mM
silver nitrate ~olution~
The fortiophore gives the alectrodes good reproducibility sd=1.72 mV for one chip, and 1.96 mV is the a~erage of two chips, and 2.10 mV i6 the 6tandard devlation across the two chips. The ~electivity over 60dium, calcium and p~ are shown to be within acceptable limit8 (see ~able 3). Wet up is ~ast (see FIG. 6), and using a calculated differPntial measure~ent (take the difference o~ eaah individual elec~rode wlth the average of the four electrodes on a chip), the wet up is very fa6t (see FIG. 7).
In order to co~pare the two layer sensor~ of the present invention having an ion ~elective membrane including a ~ortiophore and without a fortiophore, a wet up of eight chips ~, 20 (four clectrodes/ch~p~ with and without ~ortiophore and membrane~ with and without XTP~ ~as done (~able 1 membranes, and FIGS. 6, an~ 8-10). Table ~ shows the ~tandard deviation of the ~our eleatrodes on a chip, 60 sec~nd post immersion, for the eight different conditions (note that the data with fortiophore as the average of two chips, while khe data : without ~ortiophore i8 one chip). ~he data shows three important points: the of~et potential producibility is better with fortiophore present in the (if one omits the : 33.9); membranes cast on Ag rather than AgCl per~orm better;
and men~rane~ without KTPB perform slightly better (with :; regard to o~fset potential reproducibility).
Chips 2-6-1 and 2-6-7 demonstrate good offset potential reproducibility (sds of 1.72 and 3.57), and good wet ups results (FIGS. 6 and 9). FIG. 7 shows the differential measurement results of chlp 2-6-1 (the average of four electrodes minus an individual) for the first three minutes after the sensor was immersed in a 10 mmolar KCl solution~

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~able 3 summari~es the selectivity and 810pe data. ~oth sensor~ meet the requirements for selective ~easurement of potassium in a phy~iological background. The slopes are comparable to the theoretically calculated ~lopes.
Table 4 summarizes ~ome precision data taken by measuring some "mock" cals, ten aqueous "~amples", and ~hen two more "mock" cals. The precision number~ are calculated at 10, 30, 4~, and 90 seconds after the sensors were immer~ed in the sample or cal. The first two rows o~ data are the average 6tandard deviation of (four eleatrode~ on a chip v~. a Corning double junction reference electrode) ten measurements in the same solution. No data was within the 0.53 mV spe~ for sample preci6ion. ~he next two row~ of data are the average standard : deviation of (~our elec~rodes on a chip) differentially measuring the same 801ution ten times. Note ~hat th~
precision here is signi~iaantly ~et~er than vs a r~eference electrode, and meets the spëcification at 30 second~ post : immersion. The last ~wo row~ of data are also differential measurements, but across both cals and samples~ ~ote that becau~e this was a di~ferential ~ea~ur~ment, th~ o~set potential reading6 should be the same and ~he standard deviat~on result6 should al80 be low. Here th~ preci6ion i~
better than versus a re~erence electrode, but not in the specification.
The pre~erred membrane formulat~on for th~ potas~ium sensor, see Table 9, use6 ~CE a~ the fortiophore, AgBENZ as the silver salt, DUP as the plasticizer, PVC as the LUpport, and VAL as the ionophore. This me~brane, as compared to the . membrane without NTCE, has significantly lower standard ~` 30 deviation o~ the absolute potentials, and lower drlft ~at 60 seconds) due to a faster wet up ~see ~able 1 and FIGS.
17-20). ^
Similar results have also been observed for sensors incorporating variations in weight percentages of membrane components. Particular attention has been given to varying the amount of metal salt, e.g. Ag salt in the membrane. It is apparent that while the amount described is optimal, a smaller or larger amount (o.S times to Z times the amount~ still improves the results compared to no Ag salt or MTCE.

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Diffarent classe6 of ~ilver alt~ have been tried ~uch as borates, e.g. silver tetraphenyl borate, silver tetrakis p-chlorophenyl borate, ~ilver salycilate; organ~c carboxylates, e~g. ~ilver benzoate; and organic sulfonates.
Different plaskicizers have been tried including~
phthalates~ sebacates, ETH 2112, and tetra-n-hexyl-3,3',4,4'-benzhydrol tetracarboxylate~ All showed similar result~, with more lipophilic ones showing~a faster response. ~he plasticizer~ are utilized with the polymer material to obtain a more homogeneous membrane wi~h increased ~n~ernal mobility.
Plasticizere other than ~hose noted above may ~erve the ~ame purpose.
It is anticipated ~hat the use of other suitable fortiophores, e.g. neutral complexing agents~ may ~erve the same purpose and may be uti}~zed in accordance wlth the present lnvention. ~DCN and DTCE are examples of other ~ fortiophores, which are complexing agents ~or Ag ions and function in the same manner of ~TCE of the pre~erred embodiment wikh Ag as the internal reference element. See Table 5~ ~able 5 provides a ~ummary o~ potas~tum ~ensor data .s.. ~ .
with ~arious fortiophores. In all case~, the standard deviation of their of~6et potentials is ~ignificantly smaller than that observed for membranes without any ~ortiophore.
PVC is the preferred support material; however, any film forming polymeric material or any material which is capa~le of . being polymerized into a ~ilm forming material, or any : material which is cross-linkable ~nto a polymeric film may be .. ; used as a support.
Tabl.e 6 and FIG. 15 summarize the data for aalcium (Ca) sensors without fortiophore (MTCE), with fortiophore (MTCE), and with ~ortiophore (MTCE) and sllver salt. The results show that both M~CE and Ag salt-are necessary to achieve the desired results. In this case sensors with forkiophore only respond slowly~ At 60 seconds the offset potentials are not reproducible, but by ten minutes the o~fset potentials become reproducible (sd=2.1)~ The slope of sensors withouk fortiophore and sensors with fortiophore only are low due to ~. ~ , '~ , -13- 2 ~ J i~

their 810w response. When Ag i~ added to the me~brane, the response is fast, and reproduci~le. Ik i~ noted that other Ag salts have been used 6uccessfully with the calcium ~ensor.
Table 7 and FIG. 16 summarize the data for pH sensors without fortiophore (NTCE), with ~ortiophore ~MTCE~ and with fortiophore (MTCE) and AgN03. The results ~ho~, a~ above, that both NTCE and Ag salt are neces~ary to achieve the desired results. Other Ag 6alts have been u~ed ~ucces~ully with this pH sens,or.
~able 8 and FIG. 17 summarize the data for sodium ~Na) sensors, without fortiophore ~N~CE), and with fortiophore (NTCE) and AgN03. The results show the same a~ above, that MTCE and Ag are necessary ~em~rane components to achieve the desired results. Other Ag salt~ (A~pClPB), plasticizers (TOTM) and ionophores (ETH 2120, and methyl monensin) have been used with ~imilar result Table 9 and FIG~. 17-20 summarize potassium sensor data where AgBENZ is varied for wet up studies.
The invention described herein has industrial utility in the de~erfflination o~ ion con~ent or other con6titutent~ o~
test samples as will be evident to those skilled in the art.
It is particularly useful ~or determination o~ the ion activity o~ biological test samples; yet can be used in similar devices determinatlons of other te~t samples of various sources.
It is to be understood t~at various other modifications will be apparent to and can readily be made by those skilled in the art, given the disclosure hereln, without departing from the scope and material spirit o~ thls invention.

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TABI~ 1 ~MBRANE CO~PO~ITIO~
Chip Composltion (wgt. 96) Membrane Ca~t on 2-6-1 ~TCE O. 4%, VAL lo 096, Blank Ag DOP 68 . 6%, PVC 30%
2-19-1 ~IAh 1. 0%, DOP 68 . 0%, PVC 31~6 Blank Ag 2-6--7 NTCE O . 4%, VAI. 1%, DOP 68 . 2%, A~/A~Cl PVC 3~%, x~rP~ O . 3%
2-19-4 ~TAI 1. 0%, DOP 68 ~1~, Ag/AgCl PVC 30 . 6~ rPB 0. 3~
2-39-10 VAI. 100%~ PVC 30.g%, TOTM 68.1% Blank Ag 2-180-3 VA~ 10%, P~rC 30.9%t ~roq~ 68.3%, M~rCE O . 37%, AgN03 0 . 25%, KN03 0 ~ 04%
2-53-10 ~CE O . 5~ 1. 096, Blank Ag PVC 30 . 8%, TOTM 67 . 6%
2-53-9 UDCM 1.3%, V~ 1~0~, Blank Ag PVC 30.5%, T~5 670296 3--62-1 ~TCE O . 4%, X~rpClPB O 0 596, Ag/AgCl ~' ~TH1001 1.0%, PVC 30.0% TOq!~ 68.1%
30050~ CE 0.8%, IDVA 1.0%, AgNO 0.6%, Blank Ag TO~I 64 . 4%, PVC 33 0 2%, kTp~lPB O . S%

5-15-2 SHONO 1.0%, BHTCN 6996, PVC 30.û~6 Blank Ag 129-32~ CE 0.4% VAL 1~1% PVC 29.7% Blank Ag DUP 68 . 896 53-17-1 ~CE 0.4% VAL 0.9% AgBENZ 0.8% Blank Ag PVC 30~5% DUP 67.4%
129-34 6 ~rCE O . 4% VAL 1.196 PVC 29 . 7% Ag/AgBENZ
DUP 68 ~ 896 ~, ~ . . :- - , , . . . . .

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Sq~ANDARD DEVIATION OF OFFS T POTENTIl~.LS Ft)UR
EhEC~RODES ON A CHIP ( in mV) Membrane* Ag AgCl -- MTCE O . 4% 1. 96 33 ~ 9 AYg. o~ two NTCE 0~4% ~ PB (0.3%) 2.97 4.45 2 chip~
_______________________ ______________,_____ ".___~______________ 4.41 7.26 Avg. one 15~PB (0.3%) 7.80 9.13 chip ________~_____________ _~_________________________,___________ *Each Mem~xane further compri~;ing VAL - 196 PVC - 30%

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SELECTIVIq~IES AND SLOPES

log k (potassium/M~

M 2-6-1 2-6-7 Target lo Value Na+ -3.6 -3 .2 -3.6 Ca++ -3.7 -3.7 ' 2.9 H+ -3 . 4 -3 . 4 +2 . 8 Slope (mV/dec) 57. 8* 57 . 3** 59 . 2 ~ 20 : ~ ; * corrected for ~ualction poten~ial: 59 . 4 ~** corrected for ~unction potential: 58 . 9 : . . .

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PRECISION (SD in mV) Reading Taken After ~sec) 3~ 44 90 emf YS extO ref ~lectrode -w/in electrode -w/in same solution 2-6-1 1.76 1.84 1.81 1.67 2-6-7 6.55 4.01 3,10 1.72 differential emf -w/in a pair of electrodes 15 -w~in same 501ution 2-6-1 0.65 0.52 0.52 ~.50 2-6-7 1.65 1.28 1.06 0.61 across different solutions 2-6-1 1.02 0.95 0.85 0.75 2-6-7 2.~64 1.6~ 1.29 0.74 targek value~ .53____________________ ~' .

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-18- 2~ 7 TABI$ 5 SUMMARY OF POTASSIUM DATA WITH ~I~IOUS FORTTOPHORES
FORTIOPHORES

6 0 sea data NON~: MTCE UDCN DT~:E
OFFSET POTENTIAL(mV)365 . 0 565 . 0 724 . 0 766 . 5 SD 55.6 1.8 2.3 279 DRIFT (mV/min) 6 . 0 1. 4 -36. 6 -5~ . 9 SD 4.0 0.6 12.7 12.1 10 60 min data OFFSET POTENTIAL(mV) 365.5 565.7 721.6 740.2 SD 6~.7 3.2 2.4 3.9 DRIFT (mV/min) -0 . 2 -0 . 3 -0 . 2 -0 .1 SD 0.2 0.2 0.04 0.08 15 NE2~B:RANE COMPOSITIONS
Val 1. 0% 1. 0% l o 0% 1. 0%
UDCN ~ 1. 3%
DTCE ---~ ~- 0 . 6%
NTCE ---- 0 . 4%
TOTM 68.1% 68.396 67.2% 67.6%
20 PV~ 30.9% 30.0% 30.5% 30.8%
~NO3 ~ 0 3 96 *
KN03 ___0 . 0896 ~~~~ ~~~--~ membranes had an uncontrolled amount of AgN03.

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~ABLE 6 SUMMARY OF CAI.CI~N SENSOR DATA
60 ~ec data NO ~CE MTCE MTCE + Ag salt OFFSE~ POTENTIAI~~mV) 358 . 0297 . 3 413 . 3 SD 14 . ~ 18 . 33 0 8 DRIFT (mV/min) 3 0 6 10 7 3 5 10 min data 10 OFFSET POTENTIAL(mV) 37S 2 327 6 414 6 DRIFT (mV/min) -o 76 ~ 2 ~ 5 21ENBRal~ COMPOSI~IONS
15 ETH1001 1 096 0 6% 0 6%
TOTM 68 . 4% 68 . 0%68 . 0%
PVC 30.1% 29.9%~9.996 RrpClPB O 5% 0 5% 5%

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-20- 2~7~

SU~Y OF pH SENSOR DATA
60 sec data NO MTCE ~rCE MTCE ~ Ag ~alt OFFSE~ POq~ENTIAL (mV)190.4 165.6 264.0 SD 11. 4 15. 6 1. 6 DRIFT ~m~/min) 27 . 5 16 .1 1. 7 SD 6.0 9.9 1.5 10 min data OFFS~ POTENTIA~(mV) 195 . 9 159 . 7 258 . 6 SD 2.8 8.5 ~.3 DRIFI ~mV/min) --0. 9 --1. 7 0 . 02 SD 0.4 0.8 0.2 ~IBRl~NE C:ONPOSITIONS
15 TDDA 1.0~6 1.1% 1.1%
~lTCE ~ - 0 . 9% 0 . 8%
AgNo3 ;~ 0 . 01%
XTpClPB 0 . 6% 0 . 5% 0 . 5%
TV~M 65 . 7% 64 . 8~6 64 . 796 PVC ' 32.7% 32.7% 3~!.9%
2 o TDDA = Tridodecyl amine ~5 , ,~ :
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SU~RY OF SODIU~ SENSOR DATA
60 sec data NO ~TCEMTCE ~ Ag salt OFFSET POTENTIAL (m~T) 147 . 5 350 . 6 SD 16.2 0.9 DRIF~ (m~min) -1. 3 0 . 3 SD 17~6 0.7 10 min data :~ 10 OFFSET POTENTI~L (mV) 188.4 356.4 SD 3.1 2.3 DRIFT ~mV/min) -1. 5 -O. 03 SD 0.2 0,03 NEMBRZ~NE COMPOSITIONS
SHONO 1. 0%1. 096 ~TCE ---- --0 . 6 ~
BHTCH 69, 0%68 . 096 PVC 3~ . 0%29 . ~96 AgTpClPB ----- O 0 8%
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TABId~ 9 SUMMARY OF POTASSIUN SENSOR DATA

Chip # 129-34-6 129-32-1 . 53-17-1 MTCE ~TCE + Mq~CE
AgBENZ Ag8ENZ
10 min data OFFSET POTEN~IAL (mV) 136.9 452.6 515.2 SD 30.9 1.0 2.0 DRIFT (mV/min) O. 9 - O . 2 - O . 8 SD ~.5 0.1 0.1 NEMBRANE COMPOSI~IONS
V~L 1.1% 1.1% 0.9%
~CE ~ 0.4% 0.49~ 0.4%
DUP 6B . 896 68 . 89~ 67 . 496 PVC 29.7% 29.7% 30.5%
AgBENZ * O . 8 % * *

* AgBENZ plated onto Ag - 81 ectrode 2~ ** Calcula~ed from amount o~ AgB~NZ satllrated solution o~ THF
used to make up membrane ca~ting solution ..

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Claims (37)

1. A sensor device comprising:
a) an internal reference element; and b) a membrane, said membrane being disposed on said internal reference element, said membrane including a fortiophore, wherein said fortiophore provides a solid internal contact between the internal reference element and the membrane.

2. A device as described in Claim 1, wherein said device further comprises: an inert substrate, and wherein said internal reference element is disposed on said inert substrate.

3. A device as described in Claim 1, wherein said ion is a cation or anion.

4. A device as described in Claim 1, wherein said ion includes:
a. potassium:
b. sodium;
c. calcium;
d. hydrogen;
e. lithium;
f. magnesium;
g. ammonium;
h. bicarbonate; or i. carbonate.

5. A device as recited in Claim 1, wherein said internal reference element comprises: an electrically conductive material.

6. A device as recited in Claim 5, wherein said electrically conductive material includes: a metal; an alloy; or a mixture of non-metal substance(s) and a metal or alloy.

7. A sensor as recited in Claim 6, wherein said metal is a noble metal.

8. A device as recited in Claim 7, wherein said noble metal is silver.

9. A device as recited in Claim 1, wherein said membrane includes: at least one ionophore.

10. A device as recited in Claim 9 wherein said membrane further comprises: a hydrophobic organic polymer: and a plasticizer.

11. A device as recited in Claim 9, wherein said ionophore forms a complex with an ion in a test ample which interfaces said membrane with a test sample.

12. A device as recited in Claim 9, wherein said membrane further comprises: a salt of said electrically conductive material.

13. A device as recited in Claim 10, wherein said hydrophobic organic polymer includes: PVC.

14. A device as recited in Claim 10, wherein said plasticizers include: DOP; TOTM; BHTCH; ONPOE; or DUP.

15. A device as recited in Claim 1, wherein said fortiophore includes: MTCE; UDCN; or DTCE.

16. A device as recited in Claim 9, wherein said ionophore includes: VAL; ETH1001; SHONO; TDDA; or ETH 2120.

17. A process for analysis of an ion in a test sample, wherein the test sample is applied to a potentiometric sensor device comprising: a fortiophore; and an ionophore.

18. A sensor device comprising: an internal reference element; a fortiophore; and a membrane.

19. A device as recited in Claim 18, wherein said device further comprises: an inert substrate, whereon said internal reference element is disposed.

20. A device as recited in Claim 18, wherein said internal reference element is a conductive material.

21. A device as recited in Claim 20, wherein said electrically conductive material is a metal; an alloy; or a mixture of a metal or alloy and a non-metal substance(s).

22. A device as recited in Claim 21 wherein said metal is a noble metal.

23. A device as recited in Claim 18, wherein said membrane further includes: a hydrophobic organic polymer; and a plasticizer.

24. A device as recited in claim 21, wherein said device further comprises: a salt of said conductive material, said salt being disposed on said electrically conductive material.

25. A device as recited in Claim 18, wherein said device further comprises: an ionophore.

26. A device as recited in Claim 18, wherein said fortiophore is a component of said membrane, and wherein said membrane is disposed on said internal reference.

27. A device as recited in Claim 18, wherein said fortiophore is disposed between said internal reference element and said membrane.

28. A device as recited in Claim 23, wherein said hydrophobic organic polymer includes: PVC.

29. A device as recited in Claim 23, wherein said plasticizer includes: DUP; DOP; TOTM; BHTCH; or ONPOE.

30. A device as recited in Claim 18, wherein said fortiophore includes: MTCE; UDCN; or DTCE.

31. A device as recited in Claim 25, wherein said ionophore includes: VAL; ETH 1001; SHONO; TDDA; or ETH 2120.

32. A device as recited in Claim 18 wherein said fortiophore is disposed on or dispersed in said membrane.

33. A device as recited in Claim 18 wherein said fortiophore is disposed between the internal reference element and the membrane.

34. A device as recited in Claim 18 wherein said fortiophore is immobilized on said internal reference element.

35. A device as recited in Claim 25 wherein said ionophore is dispersed in said membrane.

36. A solid electrochemical internal contact for an electrochemical device comprising: a fortiophore.

37. A contact as recited in Claim 36 wherein said device comprises: an internal reference element; and a membrane, wherein said fortiophore interfaces said internal element and said membrane.